Chloroplast-genome-wide maps of small RNAs in Chinese cabbage (Brassica rapa) and Arabidopsis thaliana (Ler).. Brassica rapa subsp. chinensis

Deep sequencing provided evidence that a novel subset of small RNAs were derived from the chloroplast genome of Chinese cabbage (Brassica rapa) and Arabidopsis (Ler). The chloroplast small RNAs (csRNAs) include those derived from mRNA, rRNA, tRNA and intergenic RNA. The rRNA-derived csRNA were preferentially located at the 3'-ends of the rRNAs, while the tRNA-derived csRNAs were mainly located at 5'-termini of the tRNAs. After heat treatment, the abundance of csRNAs decreased in chinese cabbage seedlings, except those of 24 nt in length. The novel heat-responsive csRNAs and their locations in the chloroplast were verified by Northern blotting. The regulation of some csRNAs to the putative target genes were identified by real-time PCR. Our results indicated that high temperature regulated the production of some csRNAs, which may have potential roles in transcriptional or post-transcriptional regulation, and affected putative target genes expression in chloroplast. Overall design: Examination of two replicates of heat treated (HT) and control (MT) Chinese cabbage sample respectively, and one Arabidopsis (Ler) RNA sample.